Peripheral component interconnect express (PCIe) is a high-speed serial computer expansion bus standard widely used to attach various hardware devices (e.g., storage devices, network cards, sound cards, and the like) to a host central processing unit (CPU). Because the host CPU memory configurations may be vendor-specific, PCIe provides for an input/output (I/O) standard to connect various devices to the CPU. PCIe allows for a variety of improvements over older bus standards (e.g., PCI and PCI-eXtended). For example, PCIe generally allows for higher maximum system bus throughput, lower I/O pin count, smaller bus footprint, native hot-plug functionality, and other advantages.
An issue with the PCIe bus standard is that each PCIe fabric is limited by a finite amount of resources. For example, each PCIe fabric's 32-bit address memory space may not exceed 4 GB in size, and each fabric may only have a maximum of 256 bus numbers. Because PCIe operates on point-to-point serial connections, these limitations directly cap the maximum number of nodes (i.e., devices) that may be attached to a PCIe fabric. That is, bus numbers for various devices may not overlap, and each attached device requires a set of unique bus numbers to function. Various bus numbers in a PCIe fabric may be reserved for particular uses (e.g., as internal bus numbers of PCIe switches, hot-plug functionality, or the like), further limiting the number of available bus numbers.
Furthermore, a fault occurring at any component attached to a PCIe fabric may impact any other downstream or upstream components attached to the faulty component. As the number of components and software drivers attached to the PCIe fabric increases, fault handling becomes more difficult and the propagation of any faults may lead to a system-wide crash.